I want a pickup for thrash as well as instrumental rock so good lead tone and harmonics are a must. It will be in the bridge of a mahogany gibson. I play various amps so amp is not a consideration.
Both do Thrash very well and both have a great lead tone. The D-Activator is tighter, brighter, higher output and pulls off harmonics easier. The Super D sounds better for the lighter stuff to my ears though.
Check out Al Di Meola's old stuff for the Super D in that context.
Chris Broderick's sound while in Megadeth is a pretty good example of how the D-activators sound.